This invention relates to ophthalmic compositions and methods for preserving and using such compositions. More particularly, the present invention relates to ophthalmic compositions, e.g., useful in caring for contact lenses, which include one or more quaternary ammonium substituted matrix materials, e.g., as preservatives or disinfectants, and to methods for disinfecting and/or preserving using such compositions.
Various compositions, e.g., solutions, are used in association with contact lenses to ensure that the lenses may be safely, comfortably and conveniently worn. Contact lens care compositions, for example, disinfecting compositions, preserving compositions, cleaning compositions, wetting compositions, conditioning compositions and the like, often utilize at least one disinfectant or preservative, depending on the type of composition, for disinfecting or preserving contact lenses after wear or preserving the lens care composition itself. A contact lens disinfecting composition generally has sufficient antimicrobial activity so that when the composition is contacted with a lens to be disinfected, microorganisms associated with the lens are killed or otherwise removed and the contact lens is effectively disinfected within a reasonable time, e.g., in the range of about 0.1 hour to about 12 hours. A contact lens disinfecting composition may be termed a microbio-cidal composition. In contrast, a contact lens preserving composition has sufficient antimicrobial activity, often less of such activity than is present in a contact lens disinfecting composition so that when the composition is contacted with a contact lens substantially no increase in the microorganism population on the lens or in the composition is obtained. A contact lens preserving composition may be termed a microbio-static composition. Other contact lens care compositions are preserved to prevent any substantial increase in, or to gradually decrease, the population of contaminating microorganisms in the compositions and, thereby, to extend their shelf life. Some preservatives used in lens preserving compositions or in preserved compositions may also be used as disinfecting agents in lens disinfecting compositions.
Various compounds are known for use as preserving agents in contacts lens preserving compositions and preserved contact lens care compositions. Examples include thimerosal, benzalkonium chloride and chlorhexidine. However, these preserving agents are known to exhibit ocular toxicity which may result in irritation or sensitivity to the eye. The degree of ocular toxicity increases when these agents are utilized as disinfecting agents. Further, a soft contact lens, a rigid gas permeable contact lens (RGP) or a hard contact lens can absorb or adsorb these compounds. This causes the contact lens to retain the irritating compound and contributes to the eye irritation and sensitivity which may result.
Stark U.S. Pat. No. 4,525,346 discloses a contact lens disinfecting solution and preserved contact lens care compositions containing 1-tris (2-hydroxyethyl) ammonium-2-butenyl-4-poly [1-dimethyl ammonium-2-butenyl]-w-tris (2-hydroxyethyl-) ammonium the salt of which has a pharmaceutically acceptable anion. The quaternary ammonium polymer disclosed in this Stark patent is capable of causing irritation and sensitivity to some contact lens wearers.
Other conventional methods of contact lens chemical disinfection utilize one or more active disinfecting agents in an aqueous medium, for example a chlorhexidine/thimerosal solution or a relatively mild solution of hydrogen peroxide. Some of these disinfecting solutions, such as those named above, are cytotoxic and are known to be adsorbed or absorbed onto or into a contact lens and cause the lens to elicit a cytotoxic response after disinfection. For example, contact lenses which have been soaked in a disinfecting hydrogen peroxide solution are to be treated to remove residual hydrogen peroxide, e.g., by soaking in a catalase solution, before they may be comfortably and safely worn again. If residual hydrogen peroxide remains on the lenses, then irritation or injury to the eye may result.
Thus, it is readily apparent that a continuing need exists for safe and efficacious compositions that can be used as contact lens disinfecting and preserving compositions and as preserved contact lens care compositions.